Multi-Input Multi-Output (MIMO) technology is capable of improving data transmission/reception efficiency using multiple transmit antennas and multiple receive antennas instead of using a single transmit antenna and a single receive antenna. A receiver using a single antenna receives data through a single antenna path, but a receiver using multiple antennas receives data through multiple paths. Accordingly, data transfer rate and data throughput may be improved, and coverage may be expanded.
To increase multiplexing gain of MIMO operation, a MIMO transmitter may receive and use channel state information (CSI) fed back from a MIMO receiver. The receiver may determine CSI by performing channel measurement using a predetermined reference signal (RS) received from the transmitter.